Texas Instruments products are most commonly encountered in keyboards and other electronic equipment in the form of 7400-series integrated circuits. This is a family of TTL (transistor–transistor logic) chips, which are building blocks for logic circuits. Originated by Texas Instruments, many other semiconductor manufacturers have produced 7400-series chips.
Texas Instruments also made keypads as well as keyboard encoders. Full-size keyboards with their branding have been found, sourced from other manufacturers such as Alps Electric, and they appear to have been an early customer for Alps KCL/KCM series.
Keyboard encoder ICs
Texas Instruments are known to have produced two models of single-chip keyboard encoders, TMS 5000 and TMS 5001.
|TMS 5000||90||4||10||ASR-33||Few details are given in advertisements|
|TMS 5001||90||4||10||NKRO/N-key lockout||Parallel||ASCII typewriter and bit-paired
|The four encoding options are likely to be separate parts|
Little is known about the TMS 5000. The only official advertisement discovered thus far is in Electronics magazine in July 1971, where it is listed under ROMs in their MOS product listing. Model TMS 5000 JC/NC is listed as “90 × 4 Keyboard Encoder” in a 40-pin package, with a 350 mW power draw at 1 MHz. In common with other encoders, it requires both +5 V and −12 V power inputs. ROM capacity is 3600 bits, or 10 bits per character.
The chip is later mentioned in US patent 3974575 filed in June 1974. An advertisement in Popular Electronics in 1977 for the “TMS-5000” (specifically TMS 5000 NL) indicates that it is a quad-mode 90-key encoder with ASR-33 output. The advertisement also mentions the “ZA 8010 C” marking as seen on the TMS 5000 NC encoder in a Clare-Pendar–manufactured Texas Instruments Silent 700 keyboard, suggesting that the chips being sold are surplus parts. However, the Clare-Pendar keyboards used TMS 5000 NC. (“NC” and “NL” are both plastic IC packages, contrasted with the ceramic “JC” and “JL”, but the meaning of “C” and “L” is not defined.)
TMS 5000 is said to be “Compatible with Reed and Mechanical Switches”, a phrase used verbatim in the TMS 5001 specifications.
By comparison, TMS 5001 is much better documented. The preliminary specifications for TMS 5001 NL are give in the Semiconductor Memory Data Book for Design Engineers from 1975. There is no indication of how TMS 5001 differs from TMS 5000. This is also a 90-key quad-mode encoder, with 10-bit output codes. Both N-key rollover and N-key lockout are offered. In N-key lockout mode, the output code is latched onto the data lines and remains so until the key is released and the next key is pressed. In N-key rollover mode, the output code is only present on the data lines briefly after the key is pressed, in order to allow the encoder to continue looking for more keys to report.
The documentation lists four output types: ASCII in both bit-paired and typewriter modes, ASR33, and Baudot paper tape punch code. With its 3600 bits of ROM and lack of any form of encoding selector, it would seem that these are separate pre-built masks, and the customer is expected to specify their choice of mask during ordering. Separate part numbers for these four variants may exist, but the databook did not list them.
Texas Instruments filed US patent 4354068 “Long travel elastomer keyboard” in February 1980, which is very early patent for full-travel rubber dome over membrane keyboards. Even if such keyboards did go into production, Texas Instruments likely did not produce them for long, as they outsourced their keyboards from other manufacturers.
Their 914 terminal keyboards and 911 Keyboard were made instead by Micro Switch, being SW Series and SD Series respectively (the examples are dated from 1975 and 1982).
Texas Instruments are notable for some rare Alps-made keyboards:
- Part no. 2230528-001 “low profile keyboard” contains Alps keyboard assembly KCMAA001, possibly the first ever Alps KCM keyboard (this would depend on whether there was an earlier KCMBA001 or similar). The example in question has a manufacture date of August 1984. The internal keyboard assembly part number is one lower, 2230527-001. All the switches were previously stripped and cannot be seen.
- The Model 931 VDT keyboard (part no. 2229188-0002) uses Alps keyboard assembly KFCMAB021, Alps part number KCMAB002. Although the Alps part number suggests 1984, the KFCM code implies 1985 or later, and the ICs appear to be dated 1985 and 1986. This keyboard uses brown Alps switches, with a single green Alps switch (SKCLFC) for what may be caps lock (there are no keycaps).
- Part no. 2240821-0001 “Low Profile Keyboard” is notable for the use of “fat brown Alps”, a unique switch design known only from Texas Instrument keyboards. Sadly, unlike the examples above where the series name is well-known, this keyboard does not appear to contain a label with the Alps model number on it, that would give us the series name of the switches.
Keyboards for the TI-99/4A were sourced from a variety of manufacturers, with the known vendors being Alps, Futaba/Sejin, General Instrument, Mitsumi and Stackpole.
The Texas Instruments TravelMate LT286/12 keyboard was produced by Hi-Tek using a rare switch type.
In 1978, Texas Instruments appeared to be aiming to enter the Hall effect keyboard market, as a Hall effect chip maker or possibly even as a full keyboard manufacturer. The article Hall-effect chip comes on film reel (Electronics, Vol. 51 No. 5, 2nd March 1978) notes:
The magnetically activated switch on its film-carrier package is aimed squarely at the high-volume keyboard manufacturers that can afford the automated assembly equipment the sprocketed-film package demands.
The article notes that “[the] new switch also fuels rumors that TI may build alphanumeric Hall-effect keyboards for itself.” Further, these keyboards “would also probably be used in the personal computer products TI is now developing.”
The article goes on to say that “TI has tightened the new device’s specifications so that a smaller magnet will trigger the switch.” Rival manufacturers to Micro Switch notably succeeded in using far smaller magnets that those used by Micro Switch, although this may have been the result of more powerful magnets rather than more sensitive sensors.
Perhaps not co-incidentally, Texas Instruments filed two US patents for Hall effect keyboards later the same year. Both patents use the same diagrams; they depict a design very similar to Hi-Tek High Profile, although using a more conventional cruciform mount.
|US 4203093||Solid state keyswitch arrangement||1978-09-19||1980-05-13|
|US 4268814||Solid state keyboard||1978-10-26||1981-05-19|
An article in PC Magazine from 6th March 1984 (Sizing Up the Professional, on pages 240–245) describes the Texas Instrument Professional Computer. On page 242, the keyboard of this computer is described. The article notes:
The TI keyboard even feels different from the IBM PC’s, and it sounds different too. The TI Professional’s keys require only a light touch—when your fingers are about halfway down, the keys finish the stroke almost unaided and almost without a sound. Instead of springs, the TI keyboard uses a resilient plastic membrane to support its keys, which are linked to electronic system with magnetically actuated (that means nothing to wear out) Hall-effect switches, two per key.
The keyboard in the Professional Computer is nothing like the design in the patent. Possibly the “resilient membrane” refers to a rubber dome sheet, with magnets inside the domes.
Also in 1984, Texas Instruments filed a patent for a rubber dome optoelectric keyboard, using small mirrors attached to the plungers to direct light through a grid:
|US 4641026||Optically activated keyboard for digital system||1984-02-02||1987-02-03|
Presently no information has been encountered to indicate whether these were ever produced.
Klixon is a type of metal dome switch produced by Texas Instruments, used for keypads.
- The Thrust in Linear Circuits advertisement, Electronics, Vol. 44 No. 15, July 19 1971, pp. 19–24 (scanned for or by WorldRadioHistory.com
- TMS 5001 NL preliminary specifications, from the Semiconductor Memory Data Book for Design Engineers (1975) (scanned by Bitsavers)
- Electronic Parts advertisement, Popular Electronics, June 1977, from the Internet Archive